This invention relates to quantitatively measuring an individual's motor skills.
Neurophysiological movement disorders, such as Parkinson's disease and Wilson's disease, often adversely affect an individual's motor skills by slowing his movements, decreasing his reaction time and causing a tremor in his body. Other effects of the disorders include rigidity (an inability to start and plan a rapid movement), bradykinesia (an inability to reach a high terminal velocity), festination (an inability to decelerate), and dystonia (an inability to smoothly control a movement of two muscles in a specific direction). Different disorders exhibit these effects in varying degrees; for example, Parkinsonian individuals typically exhibit a fine tremor, while patients afflicted with Wilson's disease display a coarse tremor.
Movement disorders include Parkinson's disease, parkinsonism, drug induced parkinsonism, parkinson's plus syndromes, supranuclear paresis, Shy Drager disease, Lewy body disease, degenerative diseases of the basal ganglia and poisonings (e.g. by manganese, carbon monoxide, carbon disulfide, hypercalcemia, drug ingestion with MPTP or MPP+ and azide overdose). All these disorders are characterized by the symptoms described above, including tremor, disorders and slowness of movement, difficulties with balance and an inability to coordinate three dimensional hand movements.
Symptoms of movement disorder are used to diagnose a particular movement disorder exhibited by an individual, and to evaluate the extent to which the individual is afflicted with the disorder. Typical measurement techniques rely heavily upon a physician's naked eye observation of the patient's movements. For example, a common technique for evaluating the amount of tremor in a patient's hand involves observing the patient insert a small rod in a series of sequentially smaller holes in a cup. The smaller the hole into which the patient can insert the rod without touching the sides of the hole, the less tremor the patient exhibits.
Some schemes have electrical connections from the sides of each hole to a device that produces a sound each time the patient hits a side of the hole. A physician can thus quantify the patient's tremor by counting the number of times a sound is emitted from the device.
Other diagnostic tests involve placing an electronic impedance device, such as an accelerometer, on a patient's hand. As the patient moves his hand, changing electric fields in the accelerometer track the patient's hand movement. A processor analyzes the output of the accelerometer to determine the velocity and acceleration of the patient's hand during the movement. This information is later compared to data collected from normal individuals and from afflicted individuals to determine a degree to which the patient exhibits a movement disorder.
Amplitude and frequency of patient tremor has been studied by Elble et al. (Journal of Neuroscience Methods, Vol. 32, pp. 193-198, 1990). In this study, afflicted patients drew freehand shapes and characters on a digitizing tablet producing a series of samples indicating the position of the pen in the plane of the tablet. Frequency spectra of the position, velocity and acceleration of the pen produced from the samples were analyzed and compared to spectra produced by normal individuals.